Power storage device

ABSTRACT

A power storage device includes an electrode assembly, a case that houses the electrode assembly, and an insulating sheet, which insulates the electrode assembly and the case from each other. The electrode assembly has a first end face, which is orthogonal to the stacking direction, two primary faces, which are located on both sides in the stacking direction, and a tab, which extends on the first end face in the direction orthogonal to the stacking direction. The insulating sheet has a folded box shape, and further has two primary face covering portions, which respectively cover the primary faces of the electrode assembly, and non-primary-face covering portions, which cover the first end face of the electrode assembly and faces other than the primary faces thereof and are continuous with the primary face covering portions. The non-primary face covering portions overlap at least partially with each other.

FIELD OF THE INVENTION

The present invention relates to a power storage device.

BACKGROUND OF THE INVENTION

Vehicles such as electric vehicles (EVs) and plug in hybrid vehicle(PHVs) are equipped with a rechargeable battery, which is a powerstorage device that stores power fed to a drive motor. For example, therechargeable battery includes an electrode assembly having a positiveelectrode and a negative electrode, and a case that houses the electrodeassembly. An insulating sheet that covers the electrode assembly toinsulate the electrode assembly from the case may be provided. In thiscase, the insulating sheet may be shaped like a spread polygon inadvance and then, assembled such that adjacent sides are butted to housethe electrode assembly. Refer to Patent Document 1, for example.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-198663

SUMMARY OF THE INVENTION

However, in the configuration in which two sides are butted as describedabove, the electrode assembly to be covered tends to be exposed from agap. Thus, ensuring of insulation between the electrode assembly and thecase has a room for improvement.

An objective of the present invention is to provide a power storagedevice capable of improving insulation between the electrode assemblyand the case.

To achieve the foregoing objective and in accordance with one aspect ofthe present invention, a power storage device is provided that includesan electrode assembly, a case, and an insulating sheet. The electrodeassembly has a layered structure in which a positive electrode and anegative electrode are stacked. The electrode assembly is configured tohave a first end face orthogonal to a stacking direction, two primaryfaces located on both sides in the stacking direction, and a tabextending from the first end face in a direction orthogonal to thestacking direction. The case is configured to house the electrodeassembly. The insulating sheet is configured to insulate the electrodeassembly from the case. The insulating sheet is shaped like a foldedbox, has two primary-face covering portions that cover the primary facesof the electrode assembly, and has non-primary-face covering portionsthat cover the first end face of the electrode assembly and faces otherthan the primary faces and are continuous with the primary-face coveringportions. The non-primary-face covering portions overlap each other atleast partially.

With such a configuration, since the primary-face covering portions arecontinuous with the non-primary-face covering portions, no gap betweenthe portions exists. Thus, the electrode assembly is hardly exposed.Further, since the non-primary-face covering portions overlap each otherat least partially, a gap from which the electrode assembly is exposedis hardly generated between the non-primary-face covering portions. Thisimproves the insulation.

The insulating sheet in a spread state is preferably rectangular as awhole. With such a configuration, the rectangular insulating sheet ofrelatively simple shape is used to form a box shape. The insulatingsheet of complicated shape is not required, facilitating manufacturingof the insulating sheet. As a result, costs for the power storage deviceare reduced. The rectangular sheet only needs to be rectangular as awhole and for example, the sheet may be chamfered or have a recess (ahole) or projection.

The non-primary-face covering portions preferably include a bottom-facecovering portion that covers a second end face, which is an end faceopposite to the first end face of the electrode assembly, and twoside-face covering portions that cover both side faces, which are twoend faces orthogonal to the primary faces, and the second end face. Inthe insulating sheet in a spread state, the bottom-face covering portionis continuous with the primary-face covering portions and providedbetween the primary-face covering portions. In the insulating sheet inthe spread state, the primary-face covering portions and the bottom-facecovering portion constitute a rectangular base portion as a whole. Inthe insulating sheet in the spread state, the side-face coveringportions extend along sides of the base portion. The insulating sheet isfolded along each of boundary lines between the primary-face coveringportions and the bottom-face covering portion and boundary lines betweenthe base portion and the side-face covering portions to form a box.Given that a length of the electrode assembly in the stacking directionis D and an extending length of the side-face covering portions from thebase portion is W, the length D and the length W are set to satisfy arelationship of D/2<W≤D. With such a configuration, the side-facecovering portions overlap each other by folding the insulating sheetalong the boundary lines. Thereby, an overlapping area can be formed bya relatively simple operation. This limits a decrease in workability,which may be caused by improvement of the insulation.

“The extending length of the side-face covering portions from the baseportion” means the length of each of the side-face covering portions,but the side-face covering portions do not need to have the same length,and may have different lengths as long as the lengths satisfy therelational expression.

The power storage device preferably further includes a protrudingportion configured to extend, in the insulating sheet in the spreadstate, from two opposed sides of the base portion in a directionorthogonal to the extending direction of the side-face coveringportions. The protruding portion protrudes from the first end face ofthe electrode assembly in the projecting direction of the tab. With sucha configuration, the protruding portion is arranged between the tab andthe case. Thus, insulation between the tab and the case is achieved byusing the structure for insulating the electrode assembly from the case.

Given that a projecting length of the tab from the first end face is T0,and a protruding dimension of the protruding portion from the first endface is K, the length D, the length T0, and the dimension K arepreferably set to satisfy a relationship of K≥T0 and T0≤D/2. With such aconfiguration, since K≥T0, an area exposed from the protruding portionhardly is formed in the tab. This achieves insulation between the taband the case more favorably. On condition that the length D of theelectrode assembly in the stacking direction is the same, a space forthe tab is smaller in the case of T0≤D/2 than the case of T0>D/2. Thisreduces the space for the power collection structure. Further, theprotruding dimension K can be decreased by decreasing the projectinglength T0 of the tab from the first end face so as to satisfy therelationship of T0≤D/2. As a result, it is possible to reduce the sizeof the insulating sheet and, reduce costs for the insulating sheet,accordingly.

In the insulating sheet in the spread state, the side-face coveringportions preferably have incisions formed from ends of the boundarylines between the primary-face covering portions and the bottom-facecovering portion along extended lines of the boundary line. Theside-face covering portions divided into a plurality of sections by theincisions overlap each other. With such a configuration, the number offolded areas is reduced, facilitating the folding operation. Thisimproves workability while ensuring insulation.

Ends of the incisions on the side of the base portion each preferablyhave a hole. With such a configuration, the holes disperse loads appliedto the ends of the incisions on the side of the base portion when theinsulating sheet is folded. This prevents the situation in which localloads are applied to the ends to tear the insulating sheet when theinsulating sheet is folded.

The case preferably has an opening into which the electrode assembly isinserted, the electrode assembly surrounded by the insulating sheet ispreferably inserted into the opening to be housed in the case, and thenon-primary-face covering portions preferably overlap each other suchthat an area continuous with the covering portion that covers a face towhich the electrode assembly is inserted is an outermost layer. Withsuch a configuration, when the electrode assembly is inserted into theinsulating sheet, the non-primary-face covering portions are unlikely tobe caught. This reduces decrease in the insertion performance, which iscaused by overlapping of the non-primary-face covering portions.

The non-primary-face covering portions preferably include a bottom-facecovering portion that covers a second end face, which is an end faceopposite to the first end face of the electrode assembly, and thebottom-face covering portion overlaps at least partially. With such aconfiguration, the bottom-face covering portion, which is susceptible tostress, and from which the electrode assembly is easily exposed, due toinstallation manner, overlaps at least partially. This further improvesthe insulation.

The overlapping area of the bottom-face covering portions is preferablyin contact with an inner face of the case. With such a configuration,since the overlapping area of the bottom-face covering portion is incontact with the inner face of the case, even when the insulating sheetrubs against the inner face of the case at the contact area due todisplacement of the electrode assembly, the electrode assembly isunlikely to be exposed. This favorably restrains the electrode assemblyfrom being exposed by rubbing between the bottom-face covering portionand the inner face of the case.

The insulating sheet preferably covers a predetermined region of thefirst end face other than the region where the tab extends. This furtherimproves the insulation in the first end face.

The power storage device preferably further includes an electrodeterminal partially exposed from the case and a conductive memberconfigured to connect the tab to the electrode terminal. Given a lengthof the tab and the conductive member from the first end face in thedirection orthogonal to the first end face is T1, and a protrudingdimension of the protruding portion from the first end face is K, thelength D, the length T1, and the dimension K are preferably set tosatisfy a relationship of 0<T1<K<D. With this configuration, the tab andthe conductive member are wholly surrounded by the protruding portion.This further improves the insulation between the case and the set of thetab and the conductive member.

The power storage device is preferably a rechargeable battery.

Effects of the Invention

According to the present invention, insulation between the electrodeassembly and the case is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rechargeable battery according to afirst embodiment;

FIG. 2 is an exploded perspective view of an electrode assembly;

FIG. 3 is an exploded perspective view of the rechargeable battery;

FIG. 4 is a front view of a spread insulating sheet;

FIG. 5 is a partial cross-sectional view of the rechargeable battery;

FIGS. 6A to 6C are diagrams showing a procedure of attaching theinsulating sheet;

FIG. 7 is an exploded perspective view of a rechargeable batteryaccording to a second embodiment;

FIG. 8 is a front view and a partial enlarged view of a spreadinsulating sheet in the second embodiment;

FIGS. 9A and 9B are diagrams showing a procedure of attaching theinsulating sheet;

FIG. 10 is a schematic view of a cross-sectional structure of therechargeable battery;

FIG. 11 is a front view of a spread insulating sheet according to athird embodiment;

FIG. 12 is a perspective view showing the manner of attaching theinsulating sheet in the third embodiment;

FIG. 13 is a partial cross-sectional view of a rechargeable batteryaccording to a fourth embodiment;

FIG. 14 is a perspective view of an electrode assembly and an insulatingsheet;

FIG. 15 is a partial cross-sectional view showing a manner of sticking afixing tape;

FIG. 16 is a perspective view of an electrode assembly and an insulatingsheet according to a fifth embodiment;

FIG. 17 is a cross-sectional view showing cross-sectional structures ofthe electrode assembly and the insulating sheet;

FIGS. 18A to 18C are perspective views showing a procedure of attachingthe insulating sheet;

FIG. 19 is a perspective view of an electrode assembly and an insulatingsheet according to a sixth embodiment;

FIG. 20 is a front view of the spread insulating sheet;

FIGS. 21A and 21B are perspective views showing a procedure of attachingthe insulating sheet;

FIG. 22 is a cross-sectional view of a power collection structure in amodification;

FIG. 23 is a cross-sectional view of a separator and an electrodeassembly in a modification;

FIG. 24 is a perspective view showing a manner of folding an insulatingsheet in a modification;

FIG. 25 is a front view of a spread insulating sheet in a modification;

FIG. 26 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 27 is a front view of a spread insulating sheet in a modification;

FIG. 28 is a front view of a spread insulating sheet in a modification;

FIG. 29 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 30 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 31 is a front view of a spread insulating sheet in a modification;

FIG. 32 is a front view of a spread insulating sheet in a modification;

FIG. 33 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 34 is a front view of a spread insulating sheet in a modification;

FIG. 35 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 36 is a front view of a spread insulating sheet in a modification;

FIG. 37 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 38 is a front view of a spread insulating sheet in a modification;

FIG. 39 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 40 is a perspective view of an insulating sheet and an electrodeassembly in a modification;

FIG. 41 is a front view of a spread insulating sheet in a modification;and

FIG. 42 is a front view of a spread insulating sheet in a modification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A power storage device according to the present invention will bedescribed with reference to FIGS. 1 to 6. The power storage device isinstalled in a vehicle (an automobile or an industrial vehicle) andserves to drive a drive motor (an electric motor) in the vehicle. Forconvenience, in FIG. 5, the thicknesses of electrodes 21 and 22, aseparator 23, and a case 11 are illustrated as different from the actualsizes as necessary.

As shown in FIG. 1, a rechargeable battery 10 as the power storagedevice is a lithium-ion rechargeable battery, and has a metallic case 11constituting a shell for the cell. The case 11 includes a container 12shaped like a box with a bottom, in particular, a rectangularparallelepiped having an opening 12 a in one side face thereof, and alid 13 that closes the opening 12 a.

The case 11 houses an electrode assembly 14 as a charge-dischargecomponent and an electrolyte solution (not shown) as an electrolyte. Asshown in FIG. 3, the electrode assembly 14 has a shape of rectangularparallelepiped corresponding to the rectangular parallelepiped-shapedinner space of the container 12, and is dimensioned to have apredetermined gap from the inner face of the container 12 when beinghoused in the container 12.

As shown in FIG. 2, the electrode assembly 14 includes a positiveelectrode 21, a negative electrode 22, a separator 23 formed of a porousfilm through which conductive ions (lithium ions) involved in electricconduction can pass.

The electrodes 21 and 22, and the separator 23 are each a rectangularsheet. Describing in detail, the lengths of two adjacent sides (thelongitudinal length and the transverse length) of the negative electrode22 are set to be greater than the lengths (the longitudinal length andthe transverse length) of two adjacent sides of the positive electrode21. The lengths of two adjacent sides (the longitudinal length and thetransverse length) of the separator 23 are set to be greater than thelengths of two adjacent sides of the negative electrode 22. That is, thenegative electrode 22 is dimensioned to cover the sheet face of thepositive electrode 21, and the separator 23 is dimensioned to cover bothof the sheet face of the positive electrode 21 and the sheet face of thenegative electrode 22.

The positive electrode 21 includes a rectangular positive-electrodemetal foil (for example, aluminum foil) 21 a and a positive-electrodeactive material layer 21 b formed by applying a positive-electrodeactive material to the sheet face of the positive-electrode metal foil21 a. The positive-electrode active material layer 21 b is formed on thesheet face of the positive electrode 21 (the positive-electrode metalfoil 21 a) except for a positive-electrode uncoated portion 21 d thatextends along an upper end 21 c (the first end) of the positiveelectrode 21 and has a predetermined width in a direction orthogonal tothe upper end 21 c.

The negative electrode 22 includes a rectangular negative-electrodemetal foil (for example, copper foil) 22 a, which is smaller than thepositive-electrode metal foil 21 a, and a negative-electrode activematerial layer 22 b formed by applying a negative-electrode activematerial to a sheet face of the negative-electrode metal foil 22 a. Thenegative-electrode active material layer 22 b is formed on the sheetface of the negative electrode 22 (the negative-electrode metal foil 22a) except for a negative-electrode uncoated portion 22 d that extendsalong an upper end 22 c of the negative electrode 22 and has apredetermined width in a direction orthogonal to the upper end 22 c. Thenegative-electrode active material layer 22 b is larger than thepositive-electrode active material layer 21 b so as to cover the entirepositive-electrode active material layer 21 b.

The electrode assembly 14 has a layered structure in which the positiveelectrode 21 and the negative electrode 22 are stacked with theseparator 23 in between. Describing in detail, the electrodes 21 and 22and the separator 23 are stacked in the state where the entirepositive-electrode active material layer 21 b is covered with thenegative-electrode active material layer 22 b, and the positiveelectrode 21 and the negative electrode 22 are covered with theseparator 23. In this case, regions where the positive-electrode activematerial layer 21 b and the negative-electrode active material layer 22b are opposed to each other with the separator 23 in between(hereinafter referred to as opposed regions 24) contribute to charge anddischarge. The stacking direction of the electrode assembly 14, inparticular, the stacking direction of the positive electrode 21 and thenegative electrode 22 can also be described as the opposing direction ofthe opposed regions 24.

Since the separator 23 is larger than each of the electrodes 21 and 22,the outer periphery of the separator 23 protrudes outward from the outerperiphery of the negative electrode 22 and the outer periphery of thepositive electrode 21 along the sheet faces. For this reason, theelectrodes 21 and 22 are unlikely to make a short circuit.

In the configuration in which the outer periphery of the separator 23protrudes outward from the outer peripheries of the electrodes 21 and 22along the sheet faces, as shown in FIG. 3, faces 33 to 36 among faces 31to 36 of the electrode assembly 14 except for primary faces 31 and 32 onboth sides of the electrode assembly 14 in the stacking direction aredefined by end faces of the separator 23. That is, the faces 33 to 36that are end faces orthogonal to the stacking direction in the electrodeassembly 14 are flush with the end faces of the separator 23. In thiscase, as shown in FIGS. 2 and 3, a longitudinal length X1 of theseparator 23 is a longitudinal length X1 of the electrode assembly 14when viewed from the stacking direction, and a transverse length Y1 ofthe separator 23 is a transverse length Y1 of the electrode assembly 14when viewed from the stacking direction. The primary faces 31 and 32 areopposed faces located opposed to the opposed regions 24, and are largerthan the other faces 33 to 36.

As shown in FIG. 1, a positive-electrode tab 41 and a negative-electrodetab 42 project from the upper end face 36 (a first end face), which isorthogonal to the stacking direction and is located near the lid 13 inthe electrode assembly 14. As shown in FIG. 2, the positive-electrodetab 41 projects from the upper end 21 c, which extends in thelongitudinal direction of the positive electrode 21, and thenegative-electrode tab 42 projects from the upper end 22 c, whichextends in the longitudinal direction of the negative electrode 22.

As shown in FIG. 2, the electrodes 21 and 22 are stacked such that thetabs 41 and 42 of the same polarity are aligned in the stackingdirection, and the tabs of the opposite polarities do not overlap eachother in the stacking direction. As shown in FIGS. 3 and 5, thepositive-electrode tabs 41 are collected at one side in the stackingdirection of the electrode assembly 14, and are folded in the collectedstate toward the side opposite to the one side. The positive-electrodetabs 41 are electrically connected to each other by welding theoverlapping areas of the positive-electrode tabs 41. As shown in FIG. 3,the negative-electrode tabs 42 are similarly collected at one side inthe stacking direction of the electrode assembly 14, and are folded inthe collected state toward the side opposite to the one side. In thiscase, the tabs 41 and 42 project, that is, extend from the upper endface 36 in the direction orthogonal to the stacking direction. Notingthat the tabs 41 and 42 project from the upper ends 21 c, 22 c, whichextend along the longitudinal direction of the electrodes 21 and 22, thetransverse direction of the electrode assembly 14 (the separator 23)when viewed from the stacking direction is the projecting direction ofthe tabs 41 and 42. The longitudinal direction of the electrode assembly14 (the separator 23) when viewed from the stacking direction is thedirection orthogonal to the projecting direction of the tabs 41 and 42.

As shown in FIG. 3, a length Y1 in the direction orthogonal to the upperend face 36 in the electrode assembly 14, in particular, in theprojecting direction of the tabs 41 and 42 in the electrode assembly 14is set to be smaller than a height H (the standing dimension from thebottom of the container 12) of the case 11. As a result, as shown inFIG. 5, in the state where the case 11 houses the electrode assembly 14,a space S is formed between the electrode assembly 14 and the lid 13.The space S houses the tabs 41 and 42. In other words, the length Y1 inthe projecting direction of the tabs 41 and 42 in the electrode assembly14 is set to be smaller than the height H of the case 11 to form thespace S that can house the tabs 41 and 42.

Describing for confirmation, the length of each of two adjacent sides ofthe positive electrode 21 does not include the length of thepositive-electrode tab 41, and the length of each of two adjacent sidesof the negative electrode 22 does not include the length of thenegative-electrode tab 42.

As shown in FIG. 1, the rechargeable battery 10 includes apositive-electrode terminal 51 and a negative-electrode terminal 52 aselectrode terminals that can be accessed from the outside of the case11, and a positive-electrode conductive member 61 and anegative-electrode conductive member 62 that connect the terminal 51 tothe tab 41, and connect the terminal 52 to the tab 42, respectively.

As shown in FIG. 3, the positive-electrode conductive member 61 isformed by bending a rectangular metal plate to be shaped like a crank asa whole when viewed from the transverse direction. Thepositive-electrode conductive member 61 is attached such that a firstpositive-electrode part 61 a as a member on one side of the curved partin the longitudinal direction overlaps (contacts) the outermost layer ofeach positive-electrode tabs 41 from the side corresponding to the lid13, and a second positive-electrode part 61 b as a member on the otherside of the curved part in the longitudinal direction is located closerto the upper end face 36 of the electrode assembly 14 than the firstpositive-electrode part 61 a.

As shown in FIG. 1, the positive-electrode terminal 51 extends throughthe case 11 while being insulated with an insulating ring 63. Describingin detail, the positive-electrode terminal 51 is partially exposed fromthe case 11, and one end in the case 11 contacts the secondpositive-electrode part 61 b. The contact area of the tabs 41 and 42 andthe first positive-electrode part 61 a, and the contact area of thesecond positive-electrode part 61 b and the positive-electrode terminal51 are welded.

Also on the negative-electrode side, a first negative-electrode part 62a of the crank-like negative-electrode conductive member 62 contacts theoutermost layer of each negative-electrode tab 42, and a secondnegative-electrode part 62 b contacts the negative-electrode terminal 52that extends through the case 11 while being insulated with theinsulating ring 63, and each contact area is welded.

In this manner, by accessing the terminals 51 and 52, power in theelectrode assembly 14 can be taken out of the case 11, and power can befed to the electrode assembly 14.

As shown in FIG. 5, the sum of a projecting length T0 of each of thebent positive-electrode tabs 41 (the negative-electrode tabs 42) fromthe upper end face 36 and the thickness of the positive-electrodeconductive member 61 (the first positive-electrode part 61 a) (thethickness of the negative-electrode conductive member 62) is acollecting dimension T1, which defines a space required for powercollection (the connection between the terminals 51, 52 and theelectrode assembly 14). The collecting dimension T1 is set to be greaterthan half a length D in the stacking direction of the electrode assembly14 (hereinafter referred to as merely the thickness D of the electrodeassembly 14) (T1>D/2). The projecting length T0 is the length from theupper end face 36 in the direction orthogonal to the upper end face 36.In other words, the projecting length T0 is the distance between theupper end face 36 and the first positive-electrode part 61 a of thepositive-electrode conductive member 61. Noting the welded area of theoutermost layer of each positive-electrode tab 41 and thepositive-electrode conductive member 61, the projecting length T0 canalso be described as the distance between the upper end face 36 and thewelded area.

The rechargeable battery 10 includes an insulating sheet 70 thatinsulates the electrode assembly 14 from the case 11. The insulatingsheet 70 will be described below in detail.

As shown in FIG. 1, the insulating sheet 70 is shaped like a box thatcovers the faces 31 to 35 except for the upper end face 36, on which thetabs 41 and 42 extend. Describing in detail, the insulating sheet 70includes primary-face covering portions 81 and 82 that cover the primaryfaces 31 and 32 in the stacking direction of the electrode assembly 14,respectively, and a bottom-face covering portion 83 that covers a bottomface 33 (the second end face) as an end face opposite to the upper endface 36. The insulating sheet 70 further includes side-face coveringportions 84 and 85 that cover the side faces 34 and 35 as end facesorthogonal to the bottom face 33 and the primary faces 31 and 32 in thestacking direction of the electrode assembly 14, respectively. Thebottom-face covering portion 83 and the side-face covering portions 84and 85 constitute “non-primary-face covering portions”. In the presentembodiment, the bottom-face covering portion 83 corresponds to a firstnon-primary-face covering portion, and the side-face covering portions84 and 85 correspond to a second non-primary-face covering portion.

As shown in FIG. 1, the insulating sheet 70 includes a protrudingportion 86 protruding from the upper end face 36 of the electrodeassembly 14 in the projecting direction of the tabs 41 and 42. Theprotruding portion 86 is continuous with the primary-face coveringportions 81 and 82 and the side-face covering portions 84 and 85, and isshaped like a frame as a whole. The tabs 41 and 42, and the conductivemembers 61 and 62 are located within the space surrounded with theprotruding portion 86. That is, the protruding portion 86 is locatedbetween the tabs 41 and 42 and the conductive members 61 and 62, and aninner face 11 a of the case 11.

Describing each of the portions 81 to 86 of the insulating sheet 70 inthe spread state in detail, as shown in FIG. 4, the insulating sheet 70in the spread state includes a rectangular base portion 91 and anextending portion 92 that extends from the base portion 91 toward theouter periphery of the sheet face, and is rectangular as a whole. Forconvenience of description, in the following description, otherwisespecifically recited, the base portion 91 and the extending portion 92are dealt in the insulating sheet 70 in the spread state.

As shown in FIG. 4, the base portion 91 is configured of theprimary-face covering portions 81 and 82 and the bottom-face coveringportion 83. The primary-face covering portions 81 and 82 are continuouswith the bottom-face covering portion in the longitudinal direction ofthe insulating sheet 70. Describing in detail, the primary-face coveringportion 81 is continuous with the bottom-face covering portion 83 via afirst boundary line B1, and the primary-face covering portion 82 iscontinuous with the bottom-face covering portion 83 via a secondboundary line B2. That is, the bottom-face covering portion 83 islocated between the primary-face covering portions 81 and 82.

The primary-face covering portions 81 and 82 and the bottom-facecovering portion 83 take the same shape as the faces 31 to 33 to becovered of the electrode assembly 14. Describing in detail, a length X2of the primary-face covering portions 81 and 82 and the bottom-facecovering portion 83 in the direction orthogonal to the projectingdirection of the tabs 41 and 42 of the electrode assembly 14 (see FIG.4) is the same as the length X1 of the electrode assembly 14 in theprojecting direction of the tabs 41 and 42. The length X2 is atransverse length of the base portion 91.

A length Y2 of the primary-face covering portions 81 and 82 in theprojecting direction of the tabs 41 and 42 of the electrode assembly 14(see FIGS. 3 and 4) is the same as the length Y1 of the electrodeassembly 14 in the projecting direction. The length Y2 is thelongitudinal length of the primary-face covering portions 81 and 82 ofthe insulating sheet 70 in the insulating sheet 70 in the spread state.

A length Y3 of the bottom-face covering portion 83 in the stackingdirection (see FIG. 4) is the same as the thickness D of the electrodeassembly 14. The length Y3 is the longitudinal length of the bottom-facecovering portion 83 of the insulating sheet 70 in the insulating sheet70 in the spread state.

In the insulating sheet 70 in the spread state, the side-face coveringportions 84 and 85 and the protruding portion 86 are included in theextending portion 92. The side-face covering portions 84 and 85 areportions extending along a side of the base portion 91, in particular, ashort side of the base portion 91 in the insulating sheet 70. In thiscase, the side-face covering portion 84 is continuous with the baseportion 91 via a third boundary line B3, and the side-face coveringportion 85 is continuous with the base portion 91 via a fourth boundaryline B4. The boundary lines B3, B4 are long sides of the base portion91.

In the insulating sheet 70 in the spread state, a first width W as thewidth (the transverse length) of the side-face covering portions 84 and85 is set to be greater than half the thickness D of the electrodeassembly 14 and smaller than the thickness D of the electrode assembly14 (D/2<W<D).

The first width W is the length of an extending portion of the side-facecovering portions 84 and 85 from the base portion 91. In other words,the first width W is the length of the side-face covering portion 84 inthe direction orthogonal to the third boundary line B3, or the length ofthe side-face covering portion 85 in the direction orthogonal to thefourth boundary line B4.

In the insulating sheet 70 in the spread state, the protruding portion86 extends from two opposed sides of the base portion 91 (in particular,short sides of the base portion 91) in the direction orthogonal to theextending direction of the side-face covering portions 84 and 85.Describing in detail, in the spread insulating sheet 70, the protrudingportion 86 is a portion extending from a short side of the base portion91 (and the longitudinal ends of the side-face covering portions 84 and85) along the long sides. The protruding portion 86 is configured of aportion continuous with the primary-face covering portion 81 via a fifthboundary line B5 and a portion continuous with the primary-face coveringportion 82 via a sixth boundary line B6. The boundary lines B5, B6 areshort sides of the base portion 91.

A second width K as the width (the transverse length) of the protrudingportion 86 is set to be greater than the collecting dimension T1 andsmaller than the thickness D of the electrode assembly 14 (T1<K<D). Asshown in FIG. 5, the second width K is the length of the insulatingsheet 70 protruding from the upper end face 36 in the projectingdirection of the tabs 41 and 42 (the protruding dimension K). Theprotruding dimension K is the length of the protruding portion 86extending from the base portion 91. In other words, the protrudingdimension K is the length of the protruding portion 86 in the directionorthogonal to the fifth boundary line B5 or the sixth boundary line B6.

The side-face covering portions 84 and 85 are each divided into threecontinuous parts by extended lines of the boundary lines B1 and B2.Describing in detail, the side-face covering portion 84 is divided intoa first part 84 a continuous with the primary-face covering portion 81,a second part 84 b continuous with the primary-face covering portion 82,and a third part 84 c continuous with the bottom-face covering portion83. Similarly, the side-face covering portion 85 is divided into threeparts 85 a to 85 c.

As shown in FIG. 3, the insulating sheet 70 is valley-folded along theboundary lines B1 to B4 to form a box having the bottom-face coveringportion 83 as the bottom. The folding manner will be described below indetail in connection with a procedure of attaching the insulating sheet70 to the electrode assembly 14.

First, as shown in FIG. 6A, the insulating sheet 70 is attached to theelectrode assembly 14 to enclose the electrode assembly 14 from the sidecorresponding to the bottom face 33. Describing in detail, theinsulating sheet 70 is attached such that the bottom-face coveringportion 83 overlaps the bottom face 33. Then, the insulating sheet 70 isfolded along the first boundary line B1 and the second boundary line B2.Thereby, both of the primary faces 31 and 32 in the stacking directionof the electrode assembly 14 are covered with the primary-face coveringportions 81 and 82, respectively.

After that, as shown in FIG. 6B, the insulating sheet 70 is folded alongthe boundary lines B3 and B4. Thereby, the both side faces 34 and 35 ofthe electrode assembly 14 are covered with the side-face coveringportions 84 and 85, respectively. In this case, as shown in FIG. 6C, inthe side-face covering portion 84, the insulating sheet 70 (parts of theside-face covering portion 84) is partially overlapped. Describing indetail, the first part 84 a and the second part 84 b partially overlapeach other, and the parts 84 a to 84 c partially overlap in theside-face covering portion 84 on the side of the bottom-face coveringportion 83.

The overlapping manner of the parts 84 a to 84 c will be described indetail. As shown in FIG. 4, in the insulating sheet 70 in the spreadstate, a first folding line J1 extending from a first intersection ofthe first boundary line B1 and the third boundary line B3 obliquely (forexample, at forty-five degrees relative to the first boundary line B1),and a second folding line J2 extending from a second intersection of thesecond boundary line B2 and the third boundary line B3 obliquely (forexample, forty-five degrees relative to the second boundary line B2) areset. The folding lines J1 and J2 extend obliquely to be gradually awayfrom the respective intersections. As shown in FIGS. 3 and 6B, theinsulating sheet 70 is folded along the folding lines J1 and J2 and thethird boundary line B3. In this case, the parts 84 a to 84 c overlap oneanother in the state where the third part 84 c is arranged on theoutermost layer and falls within the side-face covering portion 84. Thesame applies to the parts 85 a to 85 c of the side-face covering portion85.

After that, as shown in FIG. 6C, a fixing tape 100 is affixed to bridgethe overlapping area of the parts 84 a to 84 c and the second part 84 b.Then, the electrode assembly 14 enclosed with the insulating sheet 70 isinserted into the container 12 from the bottom face 33 to be housed inthe container 12. This prevents a short circuit between respective faces31-35 except for the upper end face 36 of the electrode assembly 14 andthe container 12.

Operation of the present embodiment will now be described.

As shown in FIGS. 4 to 6, the box-like insulating sheet 70 is formed byfolding the rectangular sheet along the boundary lines B1 to B4 and thefolding lines J1 and J2, and the electrode assembly 14 is housed in thebox-like insulating sheet 70. In this case, the primary-face coveringportions 81 and 82 are continuous with the adjacent non-primary-facecovering portions (the bottom-face covering portion 83 and the side-facecovering portions 84 and 85). For this reason, no gap is formed in theboundaries of the portions 81 to 85 of the insulating sheet 70, whichcovers the faces 31 to 35 of the electrode assembly 14, to improve theinsulation.

The side-face covering portion 84 (the parts 84 a to 84 c) partiallyoverlap each other. That is, the side-face covering portion 84 isconfigured by allowing the parts 84 a to 84 c to overlap each other.Thus, the side-face covering portion 84 is unlikely to have a gap fromwhich the side face 34 of the electrode assembly 14 is exposed.

The parts 84 a to 84 c constituting the side-face covering portion 84fall within the side-face covering portion 84 without parts thereofprotruding beyond the side-face covering portion 84. Thus, when theelectrode assembly 14 is housed in the case 11, the insulating sheet 70does not become an obstacle.

In particular, if the parts 84 a to 84 c partially protrude toward theprimary-face covering portions 81 and 82, bulging portions projectingfurther than other portions are formed on the primary-face coveringportions 81 and 82, and a local load is applied to each of the bulgingportions. Then, the opposed regions 24 may be subjected to the localload, leading to disadvantages such as the precipitation of lithium. Incontrast, since the parts 84 a to 84 c are folded to fall within theside-face covering portion 84 in the present embodiment, suchdisadvantages are unlikely to occur.

Since the first width W is set to be smaller than the thickness D of theelectrode assembly 14, when the insulating sheet 70 is folded along thethird boundary line B3, the first part 84 a and the second part 84 b donot protrude outward in the stacking direction from the primary-facecovering portions 81 and 82. This eliminates the necessity of furtherfolding the first part 84 a and the second part 84 b.

In particular, the outermost layer of the overlapping area of the parts84 a to 84 c in the side-face covering portion 84 on the side of thebottom-face covering portion 83 becomes the third part 84 c, which iscontinuous with the bottom-face covering portion 83 located on theinsertion side of the electrode assembly 14 enclosed with the insulatingsheet 70. As a result, the bottom-face covering portion 83 is continuouswith the overlapping area, and ends of the parts 84 a to 84 c are notexposed when viewed from the direction opposite to the insertingdirection. Thus, at insertion, the overlapping area of the parts 84 a to84 c is unlikely to be caught.

The protruding portion 86, which protrudes from the upper end face 36 ofthe electrode assembly 14 in the projecting direction of the tabs 41 and42, is located between the tabs 41 and 42 and the conductive members 61and 62, and the case 11. This improves the insulation between the tabs41 and 42, the conductive members 61 and 62, and the case 11. Inparticular, the protruding dimension K is set to be greater than thecollecting dimension T1. For this reason, the tabs 41 and 42, and theconductive members 61 and 62 (connection structure of the electrodeassembly 14 and the terminals 51 and 52) are wholly surrounded with theprotruding portion 86. This further improves the insulation of theconnection structure from the case 11.

The present embodiment achieves the following advantages.

(1) The insulating sheet 70 is provided through folding, which is shapedlike a box with a bottom, covers the faces 31 to 35 of the electrodeassembly 14 except for the upper end face 36, and has the continuousportions 81 to 85. Thus, no gap is formed in the boundaries of theportions 81 to 85, improving the insulation.

The insulating sheet 70 includes the side-face covering portions 84 and85, which cover both side faces 34 and 35 as two end faces orthogonal toboth of the primary faces 31 and 32 among the faces 31 to 36 of theelectrode assembly 14 in the stacking direction of the electrodeassembly 14, and the upper end face 36 on which the tabs 41 and 42 areformed (and the bottom face 33 on the side opposite to the upper endface 36). In the side-face covering portion 84, the parts 84 a to 84 c,which constitute the side-face covering portion 84, partially overlapeach other. As a result, a gap from which the side face 34 of theelectrode assembly 14 is exposed is unlikely to be formed in theside-face covering portion 84. This further improves the insulation.

In particular, the insulating sheet 70 is folded such that the parts 84a to 84 c fall within the side-face covering portion 84. This preventsdisadvantages caused by the protrusion of a part of the insulating sheet70 from the primary-face covering portions 81 and 82 toward the outerside in the stacking direction, for example, a local load on the opposedregions 24. The same applies to the side-face covering portion 85.

(2) The insulating sheet 70 in the spread state is rectangular. Thisimproves the insulation without any special processing such as cuttingof the insulating sheet 70. This also simplifies manufacturing of theinsulating sheet 70, enabling use of versatile products.

(3) Further, since the box-like insulating sheet 70 with a bottom isformed by folding, the boundaries of the parts 84 a to 84 c areseamless, which prevents the formation of a gap. This further improvesthe insulation.

(4) Given that the length of the extending portion of the side-facecovering portion 84 from the base portion 91 is W, and the thickness ofthe electrode assembly 14 is D, a relationship of D/2<W<D holds. Thus,when the side-face covering portion 84 is folded along the thirdboundary line B3, parts of the side-face covering portion 84 (the parts84 a to 84 c) overlap. Therefore, the box-like insulating sheet 70having good insulation can be formed relatively easily.

(5) The insulating sheet 70 is folded such that the third part 84 c,which is continuous with the bottom-face covering portion 83, becomesthe outermost layer. The bottom-face covering portion 83 covers thebottom face 33, which is the face of the side to which the electrodeassembly 14 is inserted. Thus, insertion of the electrode assembly 14into the container 12 is unlikely to be inhibited by the overlappingarea of the insulating sheet 70. For this reason, it is possible toprevent the situation in which insertion of the electrode assembly 14 isinhibited due to partial overlapping of the insulating sheet 70.

(6) The insulating sheet 70 includes the protruding portion 86, whichprojects from the upper end face 36 in the projecting direction of thetabs 41 and 42 and surrounds the tabs 41 and 42 and the conductivemembers 61 and 62. The protruding portion 86 is located between the case11 and the set of the tabs 41 and 42 and the conductive members 61 and62. This prevents a short circuit therebetween. The use of a member forinsulating the electrode assembly 14 from the case 11 favorablyrestrains a short circuit between the tabs 41 and 42 and the conductivemembers 61 and 62, and the case 11. In particular, the protrudingdimension K is set to be greater than the collecting dimension T1.Thereby, the whole of the tabs 41 and 42 and the parts 61 a and 62 a aresurrounded with the protruding portion 86, which improves theinsulation.

Second Embodiment

A second embodiment is different from the first embodiment in theconfiguration of the case and the insulating sheet. The differences willbe described below. The same components as those in the first embodimentare given the same reference numerals and description thereof isomitted. FIG. 10 shows a case 111 and an insulating sheet 120 in across-sectional view and other components in a front view.

As shown in FIG. 7, the case 111 of a rechargeable battery 110 in thepresent embodiment includes a container 112 having an opening 112 a intowhich the electrode assembly 14 with the tabs 41 and 42 is inserted fromthe primary face 32 of the electrode assembly 14 in the stackingdirection, and a lid 113 that closes the opening 112 a. The electrodeassembly 14 is inserted into the container 112 from the primary face 32via the opening 112 a in the state where the tabs 41 and 42 are weldedto the conductive members 61 and 62, respectively, thereby being housedin the container 112. The terminals 51 and 52 are attached after theinsertion of the electrode assembly 14 into the container 112.

As shown in FIG. 7, as in the first embodiment, the insulating sheet 120in the present embodiment is shaped like a box with a bottom, andincludes primary-face covering portions 131 and 132 that cover both ofthe primary faces 31 and 32 of the electrode assembly 14 in the stackingdirection, a bottom-face covering portion 133 that covers the bottomface 33 of the electrode assembly 14, and side-face covering portions134 and 135 that cover both of the side faces 34 and 35 of the electrodeassembly 14.

The insulating sheet 120 in the present embodiment includes protrudingportions 136 and 137 protruding from the upper end face 36 of theelectrode assembly 14 in the projecting direction of the tabs 41 and 42.The protruding portions 136 and 137 have the same shape, and are opposedto each other with the tabs 41 and 42 and the conductive members 61 and62 in between. In this case, as shown in FIG. 10, a length L of theprotruding portion 137 in the longitudinal direction (the directionorthogonal to the projecting direction of the tabs 41 and 42) is greaterthan a length T2 of the area where the tabs 41 and 42 are arranged inthe same direction (the length from the upper end of thepositive-electrode tab 41 to the upper end of the negative-electrode tab42). For this reason, the tabs 41 and 42 are wholly arranged between theprotruding portions 136 and 137. The protruding dimension K of theprotruding portions 136 and 137 (see FIG. 8) is the same as that in thefirst embodiment.

The insulating sheet 120 includes a top-face covering portion 138 thatcovers a part of the upper end face 36 of the electrode assembly 14, inparticular, the area other than the tabs 41 and 42. As shown in FIG. 10,the top-face covering portion 138 is located between the secondpositive-electrode part 61 b and the electrode assembly 14, and islocated between the second negative-electrode part 62 b and theelectrode assembly 14.

Next, the folding manner of the insulating sheet 120, and the protrudingportions 136 and 137 and the top-face covering portion 138 will bedescribed with reference to the spread insulating sheet 120.

As shown in FIG. 8, the spread shape of the insulating sheet 120 in thepresent embodiment is the same as that of the insulating sheet 70 in thefirst embodiment. The insulating sheet 120 includes a base portion 141configured of the primary-face covering portions 131 and 132 and thebottom-face covering portion 133, and an extending portion 142configured of the side-face covering portions 134 and 135, theprotruding portions 136 and 137, and the top-face covering portion 138.The shape of the portions 131 to 135 is the same as the portions 81 to85 of the insulating sheet 70 in the first embodiment and thus, detaileddescription thereof is omitted.

The protruding portions 136 and 137 and the top-face covering portion138 are portions protruding from the base portion 141 and the side-facecovering portions 134 and 135 along long sides of the base portion 141in the insulating sheet 120. In this case, the width (the length in theextending direction) of the top-face covering portion 138 is the same asthe protruding dimension K of the protruding portions 136 and 137.

As shown in FIG. 8, the insulating sheet 120 has a plurality ofincisions C1 to C3. Describing in detail, the side-face coveringportions 134 and 135 have first incisions C1 cut from the ends of theboundary lines B1 and B2 along extended lines of the first boundary lineB1 and the second boundary line B2 by the first width W. In the spreadstate, the side-face covering portion 134 is divided into parts 134 a to134 c by the first incisions C1, and the parts can be individuallyfolded. The side-face covering portion 135 is similarly divided intoparts 135 a to 135 c by the first incisions C1.

The insulating sheet 120 has second incisions C2 for separating theprotruding portions 136 and 137 from the top-face covering portion 138.Describing the side of the protruding portion 136 in detail, as shown inFIG. 8, the two second incisions C2 are formed at an interval of thelongitudinal length L of the protruding portion 136. The secondincisions C2 protrude from the fifth boundary line B5 in the directionorthogonal to the fifth boundary line B5 by the protruding dimension K.Thus, the protruding portion 136 and the top-face covering portion 138can be individually folded. On the side of the protruding portion 137,the protruding portion 137 and the top-face covering portion 138 canalso be folded along the second incisions C2.

The insulating sheet 120 in the spread state has third incisions C3 cutalong extended lines of the third boundary line B3 and the fourthboundary line B4 by the protruding dimension K. Thus, in the top-facecovering portion 138, portions continuous with the primary-face coveringportions 131 and 132 and portions continuous with the side-face coveringportions 134 and 135 can be individually folded.

As shown in a partial enlarged view of FIG. 8, bottom ends (inparticular, the ends on the side corresponding to the base portion 141)of the incisions C1 to C3 each have a hole 151. The hole 151 protrudestoward the base portion 141 in a curved shape, and, in particular, iscircular. A diameter of the hole 151 is greater than the width of eachof the incisions C1 to C3.

Next, describing the folding manner of the insulating sheet 120 in thepresent embodiment, as shown in FIGS. 9A and 9B, the side-face coveringportion 134 is formed by being sequentially folded along the thirdboundary line B3 in the order of the third part 134 c, the first part134 a, and the second part 134 b. In this case, the second part 134 bcontinuous with the primary-face covering portion 132 becomes theoutermost layer, and the parts 134 a to 134 c overlap each other.Similarly for the side-face covering portion 135, the parts 135 a to 135c are folded such that the second part 135 b continuous with theprimary-face covering portion 132 becomes the outermost layer.

As shown in FIG. 9B, the top-face covering portion 138 is formed bybeing sequentially folded along the boundary lines B5 and B6 in theorder of the part continuous with the side-face covering portion 134,the part on the side corresponding to the protruding portion 136, andthe part on the side corresponding to the protruding portion 137.

As shown in FIG. 7, a fixing tape 100 is affixed to bridge the firstpart 134 a and the second part 134 b, which constitute the side-facecovering portion 134. Similarly, a fixing tape (not shown) is affixed tothe side-face covering portion 135. The fixing tape 100 is also affixedto bridge the ends of parts constituting the top-face covering portion138. Thereby, the insulating sheet 120 is attached to the electrodeassembly 14 while being restricted in displacement.

The second incisions C2 are positioned such that the protruding portions136 and 137 sandwich the tabs 41 and 42 therebetween in the stackingdirection when the electrode assembly 14 is housed in the box-likeinsulating sheet 120. Describing in detail, as shown in FIGS. 8 and 10,a distance A1 between the third incisions C3 and the second incisions C2on the side of the side-face covering portion 134 is smaller than adistance A2 between the boundary of the upper end face 36 and the sideface 34 covered with the side-face covering portion 134, and thepositive-electrode tab 41. Similarly, a distance A3 between the thirdincisions C3 and the second incisions C2 on the side of the side-facecovering portion 135 is smaller than the distance (not shown) betweenthe boundary of the upper end face 36 and the side face 35 covered withthe side-face covering portion 135, and the negative-electrode tab 42.

Operation of the present embodiment will now be described.

As shown in FIG. 8, since the side-face covering portion 134 has thefirst incisions C1, in the insulating sheet 120 in the spread state, theparts 134 a to 134 c can be individually folded. Thus, it is no need tofold the sheet along the folding lines J1 and J2 in the firstembodiment. As a result, the folding operation is simplified, and thenumber of overlapping layers is reduced.

In particular, the bottom ends of the incisions C1 to C3 each have thecurved hole 151 protruding toward the base portion 141. Thereby, infolding of the insulating sheet 120, a local load on each of the bottomends of the incisions C1 to C3 can be suppressed.

As shown in FIG. 7, the top-face covering portion 138 is folded alongthe boundary lines B5, B6 to cover the upper end face 36 of theelectrode assembly 14, and the protruding portions 136 and 137 protrudein the projecting direction of the tabs 41 and 42 without being foldedto prevent contact of the tabs 41 and 42 with the case 111.

In particular, as described in the first embodiment, the protrudingdimension K, the thickness D of the electrode assembly 14, and thecollecting dimension T1 are set to satisfy a relationship of T1<K<D. Forthis reason, the protruding portions 136 and 137 are located between thetabs 41 and 42 and the case 111. In other words, when viewed from thestacking direction of the electrode assembly 14, the tabs 41 and 42 arecovered with the protruding portions 136 and 137. Since the length ofthe top-face covering portion 138 in the extending direction is the sameas the protruding dimension K, the length is less than the thickness Dof the electrode assembly 14. For this reason, even when the parts ofthe top-face covering portion 138 are folded, the parts do not protrudeoutward in the stacking direction from the primary-face coveringportions 131 and 132.

The insulating sheet 120 overlaps such that the part continuous with theprimary-face covering portion 82 becomes the outermost layer. Theprimary-face covering portion 82 covers the primary face 32 to which theelectrode assembly 14 is inserted in the stacking direction of theelectrode assembly 14. Thus, in the configuration in which theinsulating sheet 120 encloses the electrode assembly 14, the ends of theparts 134 a to 134 c are not exposed when viewed from the directionopposite to the inserting direction. Therefore, at insertion of theelectrode assembly 14, the overlapping area of the insulating sheet 120does not become an obstacle.

In addition to the above described advantages (1), (2), (4), and (5),the present embodiment achieves the following advantages.

(7) The insulating sheet 120 has the first incisions C1 such that theparts 134 a to 134 c constituting the side-face covering portion 134 canbe individually folded. As a result, the side-face covering portion 134can be easily folded, and the number of overlapping layers is reduced.

(8) The hole 151 is formed in each of the bottom ends of the incisionsC1 to C3. This can suppress a local load from onto each bottom end. Inparticular, the hole 151 is a circle having a greater diameter than thecutting width. Thereby, the area (the circumference) subjected to stresscan be increased, which further disperses the stress.

Since the dimension of each of the incisions C1 to C3 is set to be thesame as the first width W or the protruding dimension K, when theinsulating sheet 120 is shaped like a box, gaps are formed at corners ofthe box due to the holes 151. However, the gaps are so small that thecontact of the electrode assembly 14 with the case 111 through the gapsis difficult or impossible. For this reason, the insulating sheet 120ensures insulation between the electrode assembly 14 and the case 111.That is, “box that covers faces other than the upper end face and bothend faces of the electrode assembly” does not necessarily mean thecompletely covered state, but includes a structure in which gaps areformed at corners of the box while ensuring insulation between the case111 and the electrode assembly 14.

(9) The protruding portions 136 and 137 opposed to each other via thetabs 41 and 42, and the top-face covering portion 138 that covers theupper end face 36 except for the tabs 41 and 42 are provided. Thisensures insulation between the tabs 41 and 42 and the case 111 andinsulation between the electrode assembly 14 and the conductive members61, 62.

In particular, the second positive-electrode part 61 b and the secondnegative-electrode part 62 b are located closer to the upper end face 36than the first positive-electrode part 61 a and the firstnegative-electrode part 62 a in the space S so as not to generate a deadspace (the space between the second positive-electrode part 61 b and thesecond negative-electrode part 62 b, and the upper end face 36). Forthis reason, the second positive-electrode part 61 b and the secondnegative-electrode part 62 b easily contact the upper end face 36. Incontrast, in the present embodiment, the top-face covering portion 138restricts contact of the second positive-electrode part 61 b and thesecond negative-electrode part 62 b with the upper end face 36. Thisreduces the dead space while suppressing the contact.

(10) In the insulating sheet 120 in the spread state, the protrudingportions 136 and 137, and a part of the top-face covering portion 138are portions extending along the long sides of the base portion 141.With such a configuration, the second incisions C2 for partitioning theportions are formed. Thereby, these portions can be individually folded.Therefore, the above-mentioned advantage (9) is achieved using therectangular insulating sheet 120.

(11) The protruding dimension K (and the length of the top-face coveringportion 138 in the extending direction), the thickness D of theelectrode assembly 14, and the collecting dimension T1 are set tosatisfy the relationship of T1<K<D. Thus, even when the top-facecovering portion 138 is folded, the parts constituting the top-facecovering portion 138 can be prevented from protruding outward in thestacking direction of the primary-face covering portions 131 and 132while improving the insulation between the tabs 41 and 42 and the case111 with the protruding portions 136 and 137.

Third Embodiment

A third embodiment is different from the former embodiments in theconfiguration of the insulating sheet. The difference will be describedwith reference to FIGS. 11 and 12.

As shown in FIG. 12, an insulating sheet 160 includes primary-facecovering portions 161 and 162 that cover both primary faces 31 and 32 inthe stacking direction of the electrode assembly 14, respectively, abottom-face covering portion 163 that covers the bottom face 33 of theelectrode assembly 14, and side-face covering portions 164 and 165 thatcover both side faces 34 and 35 of the electrode assembly 14,respectively. The insulating sheet 160 further includes protrudingportions 166 and 167 that protrude from the upper end face 36 of theelectrode assembly 14 and are opposed to each other so as to sandwichthe tabs 41 and 42 therebetween, and a top-face covering portion 168that covers an area of the upper end face 36 except for the tabs 41 and42.

Describing the spread shape of the insulating sheet 160, as shown inFIG. 11, the primary-face covering portions 161 and 162 and theside-face covering portion 165 constitute a rectangular base portion171. In this case, the primary-face covering portion 161 is continuouswith the side-face covering portion 165 via the first boundary line B1,and the primary-face covering portion 162 is continuous with theside-face covering portion 165 via the second boundary line B2. Atransverse length of the side-face covering portion 165 is set to be thesame as the thickness D of the electrode assembly 14.

As shown in FIG. 11, the bottom-face covering portion 163, the side-facecovering portion 164, the protruding portions 166 and 167, and thetop-face covering portion 168 constitute an extending portion 172.Describing in detail, the side-face covering portion 164 is divided intotwo parts 164 a and 164 b extending from the primary-face coveringportions 161 and 162, respectively, along long sides of the base portion171. The bottom-face covering portion 163 is a portion extending fromthe base portion 171 and the side-face covering portion 164 along oneshort side of the base portion 171. The protruding portions 166 and 167and the top-face covering portion 168 are portions extending from thebase portion 171 and the side-face covering portion 164 along the othershort side of the base portion 171. In this case, the side-face coveringportion 164 is continuous with the primary-face covering portions 161and 162 via the third boundary line B3, and the bottom-face coveringportion 163 is continuous with the base portion 171 via the fourthboundary line B4. In the present embodiment, the side-face coveringportion 165 corresponds to the first non-primary-face covering portion,and the bottom-face covering portion 163 corresponds to the secondnon-primary-face covering portion.

The width of the side-face covering portion 164 (the length in theextending direction) is set to be the first width W. Widths of thebottom-face covering portion 163, the protruding portions 166 and 167,and the top-face covering portion 168 (the length in the extendingdirection) are each set to be the protruding dimension K.

The insulating sheet 160 has first incisions C1 along extended lines ofthe first boundary line B1 and the second boundary line B2, secondincisions C2 that partition the protruding portions 166 and 167, and thetop-face covering portion 168, and third incisions C3 along an extendedline of the third boundary line B3. The bottom-face covering portion 163is divided into five parts 163 a to 163 e by the incisions C1 and C3.

As shown in FIG. 12, the insulating sheet 160 is attached to theelectrode assembly 14 from the side face 35 such that the side face 35of the electrode assembly 14 is covered with the side-face coveringportion 165, and is folded along the boundary lines B1 to B4, to form abox that covers the faces 31 to 35 of the electrode assembly 14. In thiscase, the parts 164 a and 164 b constituting the side-face coveringportion 164 partially overlap each other, and the parts 163 a to 163 econstituting the bottom-face covering portion 163 partially overlap eachother. The fixing tape 100 is affixed over the overlapping area.

Operation of the present embodiment will now be described.

In the present embodiment, adjacent ones of the portions 161 to 165 ininsulating sheet 160 are continuous with each other. The parts 164 a and164 b constituting the side-face covering portion 164 partially overlapeach other, and the parts 163 a to 163 e constituting the bottom-facecovering portion 163 partially overlap each other. This preventsexposure of the faces 31 to 35 of the electrode assembly 14. The tabs 41and 42 are sandwiched between the protruding portions 166 and 167, and apart of the upper end face 36 is covered with the top-face coveringportion 168. This achieves the above-mentioned advantages (1), (2), (4),(8) to (11).

In the present embodiment, the widths of the bottom-face coveringportion 163, the protruding portions 166 and 167 and the top-facecovering portion 168 (the length in the extending direction) are eachset to be the same value (the protruding dimension K). However, thesewidths may be different from one another in the range of values lessthan the thickness D of the electrode assembly 14.

Fourth Embodiment

A fourth embodiment is different from the former embodiments in theprojecting length T0 of the positive-electrode tab 41 from the upper endface 36 and the collecting dimension T1. The difference will bedescribed with reference to FIGS. 13 to 15.

As shown in FIG. 13, the projecting length T0 of each positive-electrodetab 41 from the upper end face 36 in the present embodiment is smallerthan half the thickness D of the electrode assembly 14. The collectingdimension T1 that is the sum of the projecting length T0 of eachpositive-electrode tab 41 and the thickness of the firstpositive-electrode part 61 a is smaller than half the thickness D of theelectrode assembly 14. A protruding dimension K of an insulating sheet180 in the present embodiment is greater than the projecting length T0of each positive-electrode tab 41 from the upper end face 36 and thecollecting dimension T1, and is smaller than half the thickness D of theelectrode assembly 14. That is, a relationship of T0<T1<K<D/2 holds.

With such a configuration, as shown in FIG. 14, the tabs 41 and 42 arelocated between protruding portions 181 and 182. A top-face coveringportion 183 covers the upper end face 36 of the electrode assembly 14without overlapping. In this case, the upper end face 36 of theelectrode assembly 14 is partially exposed. As shown in FIG. 15, thefixing tape 100 is affixed to bridge the top-face covering portion 183and the exposed area of the upper end face 36.

Operation of the present embodiment will now be described

In connection with T0<T1<D/2, the protruding dimension K is greater thanthe collecting dimension T1 and is smaller than half the thickness D ofthe electrode assembly 14. Thus, the insulating sheet 180 is smallerthan the insulating sheet 70 having K>D/2 in the first embodiment.

Due to the relationship of K<D/2, the upper end face 36 of the electrodeassembly 14 is partially exposed from the top-face covering portion 183.However, since the fixing tape 100 is affixed to bridge the exposed areaof the upper end face 36 and the top-face covering portion 183,displacement of the insulating sheet 180 from the electrode assembly 14is restricted.

In addition to the above described advantages (1), (2), (4), (5), and(7) to (10), the present embodiment achieves the following advantage.

(12) The relationship of T0<D/2 holds. Thus, as compared to theconfiguration of T0>D/2, the space for the tabs 41 and 42 is smaller,reducing the space for power collection structure.

With such a configuration, due to the relationship of K>T0, theinsulating sheet 180 can be miniaturized while arranging the tabs 41 and42 between the protruding portions 181 and 182, reducing costs for theinsulating sheet 180.

In particular, the collecting dimension T1 including the projectinglength T0 of the positive-electrode tab 41 from the upper end face 36 isset to be smaller than D/2, and the protruding dimension K is set to begreater than the collecting dimension T1 and smaller than D/2. Thus, thespace for the tabs 41 and 42 and the conductive members 61 and 62 as thepower collection structure is reduced, and insulation between thesecomponents and the case 11 is favorably ensured.

The fixing tape 100 is affixed to bridge the exposed area of the upperend face 36 of the electrode assembly 14 and the top-face coveringportion 183. This limits displacement of the insulating sheet 180 fromthe electrode assembly 14 while miniaturizing the insulating sheet 180.

Fifth Embodiment

A fifth embodiment is different from the third embodiment in the foldingmanner of the insulating sheet 160 (see FIG. 11). This will be describedbelow.

As shown in FIGS. 16 and 17, the insulating sheet 160 partially overlapson the bottom face 33 of the electrode assembly 14. Describing indetail, the second part 163 b continuous with the primary-face coveringportion 162 overlaps the first part 163 a continuous with theprimary-face covering portion 161. At one longitudinal end of thebottom-face covering portion 163, the fourth part 163 d and the fifthpart 163 e overlap the first part 163 a and the second part 163 b fromthe outer side. At the other longitudinal end of the bottom-facecovering portion 163, the third part 163 c overlaps the first part 163 aand the second part 163 b from the outer side. Then, the fixing tape 100is affixed to the overlapping parts. In this case, as shown in FIG. 17,since the third part 163 c, the fourth part 163 d, and the fifth part163 e overlap one another, both longitudinal ends of the bottom-facecovering portion 163 are thicker than the central area thereof. Thethird part 163 c and the fifth part 163 e are in contact with the innerface 11 a of the case 11. The central area of the bottom-face coveringportion 163 floats from the inner face 11 a of the case 11.

As shown in FIG. 17, since the number of overlapping layers varies inthe region between the longitudinal ends of the bottom-face coveringportion 163, the electrode assembly 14 is slightly inclined in thevertical direction. However, the thickness of the insulating sheet 160is extremely small and accordingly, the inclined angle of the electrodeassembly is negligibly small.

The folding manner of the insulating sheet 160 will be described indetail. First, as shown in FIG. 18A, the insulating sheet 160 is foldedalong the boundary lines B1 to B3 such that the parts 164 a and 164 bconstituting the side-face covering portion 164 overlap each other.Then, the first part 163 a and the second part 163 b are folded towardthe bottom face 33 of the electrode assembly 14 along the fourthboundary line B4. As shown in FIG. 18B, the third part 163 c is foldedtoward the bottom face 33, and the fourth part 163 d and the fifth part163 e is folded toward the bottom face 33. Further, as shown in FIG.18C, the fixing tape 100 is affixed to an area where ends of the thirdpart 163 c and the second part 163 b overlap each other. The fixing tape100 is affixed to an area where ends of the second part 163 b, thefourth part 163 d, and the fifth part 163 e overlap one another.

Operation of the present embodiment will now be described.

Since the overlapping area of the insulating sheet 160 in thebottom-face covering portion 163 contacts the inner face 11 a of thecase 11, when the electrode assembly 14 is displaced from the case 11,the overlapping area rubs against the inner face 11 a of the case 11.

In addition to the above described advantages (1), (2), (4), and (8) to(11), the present embodiment achieves the following advantages.

(13) The insulating sheet 160 includes the bottom-face covering portion163, which covers the bottom face 33 as an end face opposite to theupper end face 36, on which the tabs 41 and 42 of the electrode assembly14 are present. The bottom-face covering portion 163, that is, the firstpart 163 a and the second part 163 b constituting the bottom-facecovering portion 163 overlap each other and further, the parts 163 c to163 e overlap thereon. Thus, the bottom face 33 of the electrodeassembly 14 is unlikely to be exposed, improving the insulation.

In particular, the parts 163 c to 163 e overlap the first part 163 a andthe second part 163 b from the outer side, that is, the side opposite tothe electrode assembly 14. This prevents a stress of the electrodeassembly 14 from concentrating on ends of the parts 163 c to 163 e.Accordingly, an imbalance of the stress is restrained.

(14) The overlapping area of the insulating sheet 160 in the bottom-facecovering portion 163 is in contact with the inner face 11 a of the case11. Thus, even when the inner face 11 a of the case 11 rubs against theoverlapping area, the electrode assembly 14 is unlikely to be exposed.Therefore, exposure of the electrode assembly 14 caused by frictionbetween the bottom-face covering portion 163 and the inner face 11 a ofthe case 11 is favorably restrained.

(15) The insulating sheet 160 overlaps at both longitudinal ends of thebottom-face covering portion 163, which tends to be subjected to a largestress from the electrode assembly 14 as compared to the central region.With this structure, the stress of the electrode assembly 14 isfavorably absorbed, restraining breakage of the insulating sheet 160 andexposure of the electrode assembly 14.

Sixth Embodiment

As shown in FIGS. 19 and 20, an insulating sheet 190 in a sixthembodiment is folded along folding lines J11 to form a box. Theinsulating sheet 190 partially overlaps in the bottom-face coveringportion 163. In this case, as shown in FIG. 19, the number ofoverlapping layers of the insulating sheet 190 is greater at bothlongitudinal ends of the bottom-face covering portion 163 than in thecentral region.

As shown in FIG. 20, the folding lines J11 are extended lines of theboundary lines B1 to B3 and lines extending from the intersections ofthe boundary lines B1 to B3 and the fourth boundary line B4 at aninclined angle of forty-five degrees. As shown in FIG. 21A, at onelongitudinal end of the bottom-face covering portion 163, the first part163 a and the fourth part 163 d are folded toward the bottom face 33 ofthe electrode assembly 14 along the folding lines J11 such that thefourth part 163 d becomes the outer layer. Then, the second part 163 band the fifth part 163 e are folded toward the bottom face 33 of theelectrode assembly 14 along the folding lines J11 such that the fifthpart 163 e becomes the outer layer. As shown in FIG. 21B, at the otherlongitudinal end of the bottom-face covering portion 163, the third part163 c is folded toward the bottom face 33 of the electrode assembly 14in the state where the parts 163 a and 163 b are folded along thefolding lines J11. The action in the present embodiment is the same asthat in the fifth embodiment and thus, description thereof is omitted.

In addition to the above described advantages of the fifth embodiment,the present embodiment achieves the following advantages.

(16) By folding the insulating sheet 190 along the folding lines J11, anoverlapping area is formed in the bottom-face covering portion 163. Thiseliminates the necessity of providing incisions, restraining theformation of gaps to simplify processing of the insulating sheet 190.The number of overlapping layers can be increased by folding theinsulating sheet 190. Therefore, the insulation is further improved.

The above described embodiment may be modified as follows.

As a connection structure (a power collection structure), as shown inFIG. 22, each positive-electrode tab 41 may stand toward the lid 13while being inclined toward the primary face 31 in the stackingdirection of the electrode assembly 14, and a positive-electrodeconductive member 201 welded to each positive-electrode tab 41 in thestacking direction may be provided. In this case, the positive-electrodetabs 41 and the case 11 tend to cause a short circuit on the side towardwhich the positive-electrode tabs 41 are inclined, and does not tend tocause a short circuit on the opposite side. In this case, the protrudingportion 86 on the side where no short circuit occurs (the side of theprimary face 32 of the stacking direction of the electrode assembly 14)may be omitted. At this time, the standing dimension of the protrudingportion 86 from the upper end face 36 may be set to be the protrudingdimension of the positive-electrode tab 41 or more. The protrudingportion 86 itself may be omitted.

As shown in FIG. 23, a separator 202 that has notches 202 a at chamferedcorners may be used. In this case, portions that cover ends of theseparator 202 in the bottom-face covering portion 163 may be overlappingareas of the insulating sheet 160. Thereby, stresses exerted to the endsare favorably received. The electrodes 21 and 22 may be similarlychamfered. In summary, the overlapping areas of the insulating sheet maycover the ends of the bottom face 33 of the electrode assembly 14.

In the first embodiment, the electrode assembly 14 is inserted into thecontainer 12 from the bottom face 33. However, by adopting the container112 in the second embodiment, the electrode assembly 14 may be insertedinto the container 112 from the primary face 32 in the stackingdirection of the electrode assembly 14. In this case, as shown in FIG.24, the insulating sheet 70 may be folded such that the second part 84 bcontinuous with the primary-face covering portion 82 that covers theprimary face 32 becomes the outermost layer. Specifically, as shown inFIG. 25, a first folding line J3 inclined from a first intersection ofthe first boundary line B1 and the third boundary line B3 toward theside opposite to the second part 84 b by forty-five degrees, and asecond folding line J4 inclined from a second intersection of the firstboundary line B1 and the third boundary line B3 toward the first part 84a by forty-five degrees are assumed. Then, the sheet is mountain-foldedalong the first folding line J3 and valley-folded along the first part84 a and the third boundary line B3 to place the first part 84 a on theside face 34 of the electrode assembly 14. Further, the sheet ismountain-folded along the second folding line J4, and valley-foldedalong the third boundary line B3 to place the second part 84 b on thefirst part 84 a.

In each of the embodiment, the boundary lines B1 to B6 may be configuredto facilitate folding. For example, the boundary lines B1 to B6 may bethinner than the other area, or creases may be previously formed alongthe boundary lines B1 to B6.

In each of the embodiments, the first width W is set to be smaller thanthe thickness D of the electrode assembly 14. however, the first width Wmay be set to be greater than the thickness D of the electrode assembly14. In this case, the sheet may be folded again so as not to protrudeoutward in the stacking direction from the primary-face coveringportions 81 and 82.

In the first, second, and fourth embodiments, the lengths in theextending direction (the lengths in the direction orthogonal to theboundary lines B3 and B4) of the side-face covering portions 84, 134that covers the side face 34 of the electrode assembly 14 and theside-face covering portions 85, 135 that cover the side face 35 of theelectrode assembly 14 are each the same first width W. However, theselengths may be different from each other.

In the first, second, and fourth embodiments, the first width W is thesame as the protruding dimension K. However, these may be different fromeach other. For example, the protruding dimension K may be the same asthe collecting dimension T1.

The protruding dimension K may be smaller than the projecting length T0of the positive-electrode tab 41 from the upper end face 36 or thecollecting dimension T1. In this case, an insulating member forisolating the conductive members 61 and 62 from the cases 11, 111 may beprovided.

In the first embodiment, the protruding portion 86 is shaped like aframe. However, the portions continuous with the side-face coveringportions 84 and 85 may be omitted such that protruding portions 86 areopposed to each other with the distance therebetween in the stackingdirection. The same also applies to the other embodiments.

In each of the embodiments, the relationship of T1<D holds. However, arelationship of T1=D may hold. In summary, a relationship of 0<T1≤D onlyneeds to hold. Thereby, in the case where the protruding dimension K isset to be collecting dimension T1 or more to be located between the tabs41 and 42 and the cases 11, 111, the protruding dimension K can beprevented from being greater than the thickness D of the electrodeassembly 14. Therefore, in the second and third embodiments, when thetop-face covering portions 138, 168 are folded, the portion can beprevented from partially protruding from the electrode assembly 14 inthe stacking direction while ensuring insulation between the tabs 41 and42 and the cases 11, 111.

In the case of T1>D/2, when the protruding dimension K is set to be thecollecting dimension T1 or more to be located between the tabs 41 and 42and the cases 11, 111, the protruding dimension K becomes greater thanD/2. Accordingly, when being folded, the top-face covering portions 138,168 overlap, improving the insulation.

In the fourth embodiment, the relationship of T1<K<D/2 holds. However, arelationship of T1≤K≤D/2 only needs to hold. For example, a relationshipof T1≤D/2≤K may be used. In summary, a relationship of K≥T1 and T1≤D/2only needs to be satisfied.

Under the situation of T1≤D/2, for example, when a relationship of K>D/2is set such that the top-face covering portion 183 partially overlaps,the tabs 41 and 42 are located between the protruding portions 181 and182. This favorably covers the upper end face 36, and favorably isolatesthe tabs 41 and 42 from the case 11. However, in terms ofminiaturization of the insulating sheet 180, a relationship of T1≤K≤D/2is preferable.

In the fourth embodiment, the projecting length T0 of eachpositive-electrode tab 41 from the upper end face 36 may be used inplace of the collecting dimension T1. That is, a relationship of K≥T0and T0≤D/2 only needs to hold, and for example, a relationship ofT1>K≥T0 and T0≤D/2<T1 may hold.

In the second embodiment, the third incisions C3 are formed along thethird boundary line B3 and the fourth boundary line B4. However, thethird incisions C3 may be formed along the fifth boundary line B5 andthe sixth boundary line B6. In summary, the incision only needs to beformed from a corner at which two intersecting sides cross each other inthe boundary lines B3 to B6 of the base portion 141 and the extendingportion 142 along one of the two sides.

In the second embodiment, the dimension of each of the incisions C1 toC3 is the first width W or the protruding dimension K and however, maybe smaller than the first width W or the protruding dimension K. In thiscase, corners of the box-like insulating sheet 120 have no gap caused bythe holes 151, and overlapping areas cover the holes 151. This furtherimproves the insulation.

In the second embodiment, the hole 151 is circular. However, the hole151 may take any shape as long as it protrudes toward the base portion141 in a curved shape. For example, the hole may be elliptic. Althoughthe diameter of the hole 151 is set to be greater than the width of eachof the incisions C1 to C3, they may be identical. The holes 151 may beomitted.

In the third embodiment, the incisions C1 to C3 are formed. However, theincisions C1 to C3 may be omitted. In this case, as in the firstembodiment, the insulating sheet 160 is folded into a box shape.

The insulating sheets 70, 120, 160, 180, and 190 may be square. Insummary, the insulating sheet only needs to be rectangular. In thiscase, the insulating sheet need not be exactly rectangular, and may havea notch or protrusion. In summary, by folding, the insulating sheet onlyneeds to be shaped like a box that can cover the faces 31 to 35 of theelectrode assembly 14 except for the upper end face 36, and hascontinuous covering portions (no gap from which the electrode assembly14 is exposed).

In each of the embodiments, the relationship of W<D holds. However, arelationship of W≤D only needs to hold. In the case of W=D, the fixingtape 100 is difficult to fall within the side-face covering portion 84and thus, W<D, which ensures the region for the fixing tape 100, is morepreferable.

In the fifth embodiment, the relationship of K=D and W=D/2 may hold. Inthis case, the insulating sheet 160 does not overlap in the side-facecovering portion 164, while the insulating sheet 160 overlaps in atleast two layers in the bottom-face covering portion 163. Describing indetail, the first part 163 a and the second part 163 b wholly overlapeach other. Accordingly, at the center of the bottom-face coveringportion 163, the insulating sheet 160 overlaps in two layers. The fourthpart 163 d and the fifth part 163 e, which do not overlap each other,overlap the first part 163 a and the second part 163 b. That is, at onelongitudinal end of the bottom-face covering portion 163, the insulatingsheet 160 overlaps in three layers. On the other hand, the third part163 c overlaps the first part 163 a and the second part 163 b, and atthe other longitudinal end of the bottom-face covering portion 163, theinsulating sheet 160 overlaps in three layers. In this manner, in thebottom-face covering portion 163, a variation in the number ofoverlapping layers of the insulating sheet 160 in the region between thelongitudinal ends is limited.

In the fifth embodiment, a relationship of K=W=D may hold. In this case,the insulating sheet 160 can overlap in four layers at the upperlongitudinal end of the bottom-face covering portion 163.

As shown in FIGS. 26 and 27, the triangular third part 163 c may overlapthe first part 163 a and the second part 163 b. In this case, as shownin FIG. 27, the bottom-face covering portion 163 of the insulating sheet190 has a plurality of incisions C10. The incisions C10 extend obliquelyfrom an intersection of the first boundary line B1 and the fourthboundary line B4, an intersection of the second boundary line B2 and thefourth boundary line B4, and an intersection of the third boundary lineB3 and the fourth boundary line B4. In this case, the third part 163 cis a triangle having a V-shaped contour, and the fourth part 163 d andthe fifth part 163 e are trapezoidal. Folding lines J12 are present onextended lines of the boundary lines B1 to B3. The insulating sheet 190is folded such that the third part 163 c becomes the outermost layer,and is folded along the folding lines J12 such that the fifth part 163 eoverlaps the fourth part 163 d to form a box. In this case, the foldinglines J12 overlap the edge of the electrode assembly 14, and theinsulating sheet 190 overlaps at the edge, which improves theinsulation.

As shown in FIG. 28, folding lines J13 having the same inclinationdirection may be defined. In this case, unlike the folding lines J11 inFIG. 20, the folding line J13 is arranged on the third part 163 c. Alsoin this case, as shown in FIG. 29, overlapping areas of the insulatingsheet 190 are formed in the bottom-face covering portion 163.

As shown in FIG. 30, the side-face covering portions 84 and 85 mayinclude overlapping first parts 84 a and 85 a and overlapping secondparts 84 b and 85 b, and a bottom-face covering portion 203 may includeoverlapping first part 203 a and second parts 203 b. In this case, theoverlapping areas of the insulating sheet 70 exist in both of thebottom-face covering portion 203 and the side-face covering portion 84.This further improves the insulation. In this modification, thebottom-face covering portion 83 in the first embodiment is replaced withthe first part 203 a, and the third parts 84 c and 85 c in the firstembodiment are replaced with the second parts 203 b. As an example ofattaching the insulating sheet 70 as described above, as shown in FIG.31, the insulating sheet 70 includes incisions C11 for dividing thesecond part 203 b into two and incisions C12 for separating the firstpart 203 a from the second part 203 b. In this case, the insulatingsheet 70 is folded such that the divided second parts 203 b overlap thefirst part 203 a.

As shown in FIG. 32, incisions C13 for separating the second part 203 bfrom the first parts 84 a and 85 a, and incisions C14 for separating thesecond part 203 b from the second parts 84 b and 85 b may be formed. Inthis case, the second parts 203 b are folded toward the first part 203a. As a result, as shown in FIG. 33, overlapping areas of the insulatingsheet 70 are formed in the bottom-face covering portion 203.

As shown in FIG. 34, incisions C15 for separating the second part 203 bfrom the second parts 84 b and 85 b and incisions C16 for separating thesecond part 203 b from the first part 203 a may be provided. Also inthis case, as shown in FIG. 35, by folding the second parts 203 b towardthe first part 203 a, overlapping areas of the insulating sheet 70 aregenerated in the bottom-face covering portion 203.

Similarly, as shown in FIG. 36, incisions C17 for separating the secondpart 203 b from the first parts 84 a and 85 a and incisions C18 forseparating the second part 203 b from the first part 203 a may beprovided. Also in this case, as shown in FIG. 37, by folding the secondparts 203 b toward the first part 203 a, overlapping areas of theinsulating sheet 70 are generated in the bottom-face covering portion203.

As shown in FIG. 38, an insulating sheet 210 may be adopted, in whichthe second parts 203 b are omitted, and a length Y3 of a bottom-facecovering portion 213 in the spread state is set to be greater than thethickness D of the electrode assembly 14, in particular, three times ofthe thickness D. In this case, as shown in FIG. 39, the insulating sheet210 may be accordion-folded in the bottom-face covering portion 213.

As shown in FIG. 40, an insulating sheet 220 may partially overlap atthe central region of a bottom-face covering portion 223 rather thanboth longitudinal ends. As shown in FIGS. 40 and 41, the insulatingsheet 220 includes a first part 223 a continuous with the primary-facecovering portion 161 and a second part 223 b continuous with theprimary-face covering portion 162. The first part 223 a and the bottomface 33 of the electrode assembly 14 have the same shape. The secondpart 223 b is smaller than the bottom face 33 of the electrode assembly14, and extends in the transverse direction from the center of an end inthe transverse direction of the primary-face covering portion 162. Thesecond part 223 b overlaps the first part 223 a to form the bottom-facecovering portion 223.

In the sixth embodiment, as shown in FIG. 20, the folding line J11 isnot present on the third part 163 c. However, for example, as shown inFIG. 42, a folding line J14 may be present on the third part 163 c. Thatis, even when the folding line is inclined in either direction, theinsulating sheet 190 overlaps in the bottom-face covering portion 163.In summary, as long as the insulating sheet is shaped like a folded box,specific positions of the folding lines may be appropriately changed.

In each of the embodiments, the fixing tape 100 is used to fix theinsulating sheets 70, 120, 160, 180, and 190. However, any fixing meansmay be adopted. For example, the sheets may be fixed by welding orsawing.

In the second and third embodiments, top-face covering portions 138 and168 cover the upper end face 36 of the electrode assembly 14 except forthe tabs 41 and 42 and however, only need to cover any area except forthe tabs 41 and 42, and may partially cover a part of the area exceptfor the tabs 41 and 42 as in the fourth embodiment.

The electrode assembly is not limited to a so-called layered electrodeassembly, but may be a so-called wound electrode assembly. In summary,the electrode assembly may take any shape as long as it can be housed inthe box-like insulating sheet.

In each of the embodiments, the negative electrode 22 is smaller thanthe separator 23. However, they may take the same shape. In this case,end faces of the negative electrode 22 and end faces of the separator 23define the faces 33 to 36 of the electrode assembly 14.

The separator 23 may use any material as long as it is a porous filmthrough which lithium ions can pass while suppressing a short circuit ofeach of the electrodes 21 and 22. For example, a porous polymer filmmade of polyolefin including polyethylene or multiple films thereof, ora film having both ceramic-coated faces may be used.

The positive electrode, the negative electrode, and the separator may besquare. They are not limited to be rectangular, but may be polygonalother than tetragon or may be elliptic.

In each of the embodiments, the rechargeable batteries 10, 110 are eachthe lithium-ion rechargeable battery. However, the batteries 10, 110 maybe other rechargeable batteries such as a nickel-hydride cell. Insummary, any battery in which ions move between a positive-electrodeactive material layer and a negative-electrode active material layer togive and receive electrical charge may be used.

The present invention may apply to other power storage devices such asan electric double layer capacitor.

In each of the embodiments, the rechargeable batteries 10, 110 areinstalled in a vehicle, but, may be installed in other devices.

The technical ideas obtainable from the above embodiments andmodifications other than those disclosed in the claim section aredescribed below.

(1) A power storage device including:

an electrode assembly that has an opposed region, where apositive-electrode active material layer is opposed to anegative-electrode active material layer, and a first end face in adirection orthogonal to an opposing direction of the opposed region, thefirst end face having a tab projecting therefrom;

a case that houses the electrode assembly; and

an insulating sheet that insulates the electrode assembly from the case,

the power storage device being characterized in that the insulatingsheet is folded into a box having two primary-face covering portionsthat cover respective primary faces located on both sides in theopposing direction of the electrode assembly, and non-primary-facecovering portions that are continuous with the primary-face coveringportions, are orthogonal to the opposing direction of the electrodeassembly, and cover faces other than the first end face, and

the insulating sheet partially overlaps in the non-primary-face coveringportions.

(2) The power storage device according to the technical concept (1),characterized in that the non-primary-face covering portions includes

a first non-primary-face covering portion that is continuous with bothof the primary-face covering portions and constitutes a rectangular baseportion along with the primary-face covering portions in the insulatingsheet in the spread state, and

a second non-primary-face covering portion that extends to one side ofthe base portion in the insulating sheet in the spread state, wherein

the second non-primary-face covering portion is configured of a firstpart and a second part, which are continuous with the primary-facecovering portions, and a third part continuous with the firstnon-primary-face covering portion,

the insulating sheet is folded along boundary lines of the primary-facecovering portions, the first non-primary-face covering portion, and thesecond non-primary-face covering portion to form a box, and

the parts overlap at least partially with each other in the box-likeinsulating sheet.

(3) The power storage device according to the technical concept (2),characterized in that the length of the second non-primary-face coveringportion in a direction orthogonal to the boundary line between thesecond non-primary-face covering portion and the base portion is greaterthan half the length of the electrode assembly in the stackingdirection, and is less than or equal to the length of the electrodeassembly in the stacking direction.

DESCRIPTION OF THE REFERENCE NUMERALS

10, 110 . . . rechargeable battery (power storage device), 11 . . .case, 12, 112 . . . container, 12 a, 112 a . . . opening of container,14 . . . electrode assembly, 21 b . . . positive-electrode activematerial layer, 22 b . . . negative-electrode active material layer, 24. . . opposed region, 31, 32 . . . primary face of electrode assembly,33 . . . bottom face (second end face) of electrode assembly, 34, 35 . .. side face of electrode assembly, 36 . . . upper end face (first endface) of electrode assembly, 41 . . . positive-electrode tab, 42 . . .negative-electrode tab, 51 . . . positive-electrode terminal, 52 . . .negative-electrode terminal, 61 . . . positive-electrode conductivemember, 62 . . . negative-electrode conductive member, 70 . . .insulating sheet, 81, 82, 131, 132, 161, 162 . . . primary-face coveringportions, 83, 133, 163, 203, 213, 223 . . . bottom-face covering portion(non-primary-face covering portion), 84, 85, 134, 135, 164, 165 . . .side-face covering portions (non-primary-face covering portions), 86 . .. protruding portion, 91, 141, 171 . . . base portion, 111 . . . case inthe second embodiment, 120 . . . insulating sheet in the secondembodiment, 136, 137, 166, 167, 181, 182 . . . protruding portions, 138,168, 183 . . . top-face covering portion (non-primary-face coveringportion), 151 . . . hole, 160 . . . insulating sheet in the third andfifth embodiments, 180 . . . insulating sheet in the fourth embodiment,190 . . . insulating sheet in the sixth embodiment, 210, 220 . . .insulating sheet in a modification, B1 to B6 . . . boundary line, C1 toC3, C11 to C18 . . . incision, J1 to J4, J11 to J14 . . . folding line,D . . . thickness of electrode assembly, W . . . first width, K . . .protruding dimension.

The invention claimed is:
 1. A power storage device comprising: anelectrode assembly with a layered structure in which a positiveelectrode and a negative electrode are stacked, the electrode assemblybeing configured to have a first end face parallel with a stackingdirection, two primary faces located on both sides in the stackingdirection, and a tab extending from the first end face in a directionorthogonal to the stacking direction; a case configured to house theelectrode assembly; and an insulating sheet configured to insulate theelectrode assembly from the case, wherein the insulating sheet is shapedlike a folded box, has two primary-face covering portions that cover theprimary faces of the electrode assembly, and has non-primary-facecovering portions that cover the first end face of the electrodeassembly and faces other than the primary faces and are continuous withthe primary-face covering portions, at least one of the non-primary-facecovering portions has parts that overlap in layers at least partially,the non-primary-face covering portions include a bottom-face coveringportion that covers a second end face, which is an end face opposite tothe first end face of the electrode assembly, and two side-face coveringportions that cover both side faces, which are two end faces orthogonalto the primary faces, and the second end face, in the insulating sheetin a spread state, the bottom-face covering portion is continuous withthe primary-face covering portions and provided between the primary-facecovering portions, in the insulating sheet in the spread state, theprimary-face covering portions and the bottom-face covering portionconstitute a rectangular base portion as a whole, in the insulatingsheet in the spread state, the side-face covering portions extend alongsides of the base portion, in the insulating sheet in the spread state,the insulating sheet further comprises a protruding portion configuredto extend from two opposed sides of the base portion in a directionorthogonal to an extending direction of the side-face covering portions,the insulating sheet is folded along each of boundary lines between theprimary-face covering portions and the bottom-face covering portion andboundary lines between the base portion and the side-face coveringportions to form a box, and given that a length of the electrodeassembly in the stacking direction is D and an extending length of theside-face covering portions from the base portion is W, the length D andthe length W are set to satisfy a relationship of D/2<W≤D, in a foldedstate in which the insulating sheet is folded to shape like a box, theprotruding portion entirely protrudes from the primary-face coveringportion in a same direction as a projecting direction of the tab, and islocated between the tab and the case, and given that a projecting lengthof the tab from the first end face is T0, and a protruding dimension ofthe protruding portion from the first end face is K, the length T0 andthe dimension K are set to satisfy a relationship of K≥T0.
 2. The powerstorage device according to claim 1, wherein the insulating sheet in aspread state is rectangular as a whole.
 3. The power storage deviceaccording to claim 2, wherein the insulating sheet is folded without anyincision to cover each face except for the upper end of the electrodeassembly.
 4. The power storage device according to claim 1, wherein, thelength D and the length T0 are set to satisfy a relationship of T0≤D/2.5. The power storage device according to claim 1, wherein in theinsulating sheet in the spread state, the side-face covering portionshave incisions formed from ends of the boundary lines between theprimary-face covering portions and the bottom-face covering portionalong extended lines of the boundary line, and the side-face coveringportions divided into a plurality of sections by the incisions overlapeach other.
 6. The power storage device according to claim 5, whereinends of the incisions on the side of the base portion each have a hole.7. The power storage device according to claim 1, wherein the case hasan opening into which the electrode assembly is inserted, the electrodeassembly surrounded by the insulating sheet is inserted into the openingto be housed in the case, and the parts of the non-primary-face coveringportions overlap in layers such that one of the parts that is continuouswith the bottom-face covering portion that covers the second end facefrom which the electrode assembly is inserted into the case is anoutermost layer of the parts.
 8. The power storage device according toclaim 1, wherein the bottom-face covering portion has parts that overlapat least partially.
 9. The power storage device according to claim 8,wherein an overlapping area of the parts of the bottom-face coveringportion is in contact with an inner face of the case.
 10. The powerstorage device according to claim 1, wherein the insulating sheet coversa predetermined region of the first end face other than the region wherethe tab extends.
 11. The power storage device according to claim 1,further comprising: an electrode terminal partially exposed from thecase; and a conductive member configured to connect the tab to theelectrode terminal, wherein, given a length of the tab and theconductive member from the first end face in the direction orthogonal tothe first end face is T1, and a protruding dimension of the protrudingportion from the first end face is K, the length D, the length T1, andthe dimension K are set to satisfy a relationship of 0<T1<K<D.
 12. Thepower storage device according to claim 1, wherein the power storagedevice is a rechargeable battery.
 13. The power storage device accordingto claim 1, wherein the boundary lines for folding are configured to bethinner than other areas of the insulating sheet.